New Solar Cell Works Rain or Shine

Rain can put a damper on solar panels. But researchers at Soochow University in China have made a hybrid solar cell that works in gloomy weather: it generates electricity from the movement of raindrops sliding on its surface.

The new device, reported in the journal ACS Nano, has two parts. There is a traditional solar cell on the bottom. On top is a device called a triboelectric generator, which converts motion into electricity.

Triboelectricity is the phenomenon behind static electricity. When two different materials rub against each other, they cause electrons to move from one to the other. This builds up opposite charges on the surfaces, creating a small electric current.

Researchers have harnessed the triboelectric effect using tiny generators that produce electricity from the rustling clothes, muscle movement, and sound vibrations.

To make the new device, the researchers put two different kinds of transparent plastic layers on top of a silicon solar cell. The layers act as a simple triboelectric generator. When water drops fall on the device and start rolling off, the plastic sheets come in contact with one another, generating electricity. Because the sheets are transparent, the solar cell still works when it is sunny.

Others have made similar hybrid generators that harness the sun and the wind. But the new device is simpler and more compact, the researchers say, because both the solar cell and triboelectric generator share one of the plastic layers as an electrode.

The output of the device is pretty low at a current of about 33 nanoamperes and voltage of around 2.14V. Nevertheless, say the researchers, the design demonstrates “a new concept in utilization of energy during various weather conditions.”